Drillable limit plug



Aug. 28, 1962 B, Q. BARRINGTON DRILLABLE LIMIT PUG Filed Jan. 50, 1959 w w .l N F f Z J ma. w T z 22 w mf I Hm P, lJ ME? Mi:

FIG. 3.

INVENTOR Burchus Q. Barringon BY w JIM.

FI .l.

ATTORNEY flhzdl Patented ug. 28, 1962 3,051,241 DRILLABLE LIMIT PUG Burchus Q. Barrington, Duncan, Olda., assignor to Halliburton Company, a corporation of Delaware Filed Jan. 30, 1959, Ser. No. 790,136 4 Claims. (Cl. 166-143) This invention relates to packing devices for use in oil Wells or the like and more particularly to drillable devices designed to be det-achably run on tubing for etfecting a Seal between the lower end of the tubing and the casing in a well, and which are known in the art as limit plugs.

In accordance with known practice, a squeeze cementing operation is commonly carried out in a well by pumping the cement slurry under high pressure down through tubing and a limit plug. After delivery of the slurry to the desired point in the well, the tubing is released from the plug. The limit plug is left in the well and holds the slurry in place until the cement sets. The limit plug and such portion of the cement as remains inside the casing has then to be drilled out, in order to put the well in condition for production.

In limit plugs heretofore designed for this purpose, metal slips have been provided to fasten the plug to the casing during the time that the squeeze cement operation is going on and while the plug is holding the cement slurry in place. Since the slips are subjected to considerable Stress, due to the high fiuid pressure on the slurry, the teeth of the slips have to be made of strong material, and this makes it difiicult to dr-ill them up after the cement has set.

In accordance with the present invention, no slips are provided on the limit plug. It has been discovered that fiexible material, such as rubber, if designed'in a particular manner, can be caused to hold the limit plug in place 'in the casing without the use of slips being necessary. Metal parts are used to back up or hold the rubber in place, but this metal may be cast iron or other metal which is comparatively easy to drill up, and hence a more Practical limit plug has been devised.

The objects of the invention will be apparent to those skilled in the art from what has been said above, and from consideration of the following detailed description of the invention, when taken in connection with the accompanying drawing, in which:

FIGURE 1 is a side view of a limit plug constructed in accordance with the principles of the invention, a quarter-section being cut away to show the internal construction, the view illustrating the position of the parts 'as it is being run into the well;

FIGURE 2 is a view in Vertical quarter section of the limit plug of FIGURE l, but showing the position of the parts after the packer is set and during a fiuid pressure operation, such as squeeze cementing;

FIGURE 3 is a view in Vertical quarter section of the limit plug of FIGURES 1 and 2, but showing the position of the parts just after the tubing has been disconnected from the limit plug.

Refern'ng to the drawing in detail, it will be seen that the limit plug is shown attached to tubing 3 and located in a casing 9 of an oil well.

The limit plug includes a mandrel having threesections permanently screwed together, these being designated 10, 11 and 12. The upper section 1G is provided with internal threads so that it may be `Secured to the tubing 8. The intermediate section 11 is of somewhat reduced diameter and serves as a coupling between the upper section and the lower section 12 which serves as a depending tube or conduit commonly called a Stinger. 'Ihe stinger 12 is of still smaller diameter than the section 11.

' There is a sleeve 13 slidably mounted on the sections 11 and 12 of the mandrel, this sleeve having two different internal diameters so 'as to fit snugly on both sections '11 and 12 and still provide a shoulder to limit upwa'rd movement of the sleeve 13 on the maudrel.

Suitable packing may be provided, as illustrated, to prevent leakage of fluid between the sleeve 13 and the mandrel section 11.

There is always some Vertical play permissible between the sleeve 13 land the maudrel. However, it will be seen that in FIGURES 1 and 2, the sleeve 13 is loosely coupled or linked to the mandrel by the tension ring 14.

The upper end of the ring 14 has an inwardly directed flange 25 which serves as an anvil for jar action when engaged by the shoulder or hammer 26 of the mandrel section 11, when the mandrel is picked up with respect to the sleeve 13, as shown in FIGURE 3.

The lower end of the tension ring 114 is threaded to the sleeve 13. The ring 14 includes a portion 15 of reduced or weakened section which parts when subjected to tension or jar action, as illustrated in FIGURE 3.

There is a wedge body 16, tapered downwardly and outwardly, permanently fixed on the lower end of the sleeve 13.

As noted above, the sleeve 13 and wedge body 16 may be made of drillable material such as cast iron.

At the bottom of this body 16, a check valve is` drel is disconnected -from the sleeve 13 and raised, thevalve closes, as shown in FIGURE 3. An O-ring or like gasket may lbe used in the valve, as illustrated, but, of course, any other known means to prevent leakage may be used, if desired. In FIGURE 3, the Stinger 12 has been raised sufiiciently to permit the valve 19 to move |into contact with the valve seat 17. When this occurs, the O-ring carried in the valve seat 17 forms a fluid-tight seal with the valve 19.

Also mounted on the wedge body 16 is a downwardly facing swab cup 20, made of rubber or other flexible material. The cup 20 is firmly attached to the wedge body 16. As previously described, the wedge body '16 is attached to the sleeve 13, so that whenever there is fiuid pressure in the oasing below the limit plug greater than the fiuid pressure in the casing above it, the cup 20, body 16 and sleeve 13 will tend to move upwardly as a unit.

The main feature of the invention resdes in the packer element actuated by the wedge body 116. This packer is made of rubber or other flexible material and consists essentially of a rather long, tapered, downwardly extending and outwardly fiared cup 21 and a fiexible, outwardly extending flange or lip 22 located just above it.

The lip 22 is quite flexible. It may bend up, as shown in FIGURE l, or it may be bent down and squeezed in between the top of the cup 21 and the ca'sing, as shown in FIGURES 2 and 3. Due to its flexibility, the lip 22 will snap downwardly to the position shown in FIGURE 2 When the packer is moved upwardly from the position of FIGURE 1. The lip 22 is in frictional engagement with the casing at all times, whether in the position of FIGURE 1 or the position of FIGURE 2.

In addition, the packer may be provided with an integral, upwardly facng cup 23. However, while the cup 23 serves a useful purpose in some Operations, it is not necessary in other Operations, and the invention should not be regarded as limited to the inclusion of the cup 23 on the packer.

It will be seen from the drawing that the packer is not attached to the sleeve 13 or to the maudrel. -It is freev 3 the mandrel is provided with a stop ring 24 to limit upward movement of the packer with respect to the mandrel.

While the limit plug of the invention may be used in other than oil well cementing Operations, its operation will be described in connection with a typical squeeze cementing job.

With the parts of the limit plug shown in FIGURE l assembled on tubing, it may be lowered down through the casing 9 of a well bore. As the mandrel is lowered, the portions 2,2 and -23 of the packer will have some friction with the casing 9, so that the packer will be in a position above that shown in FIGURE l, but be pushed down through the casing by the shoulder 24. If the cup 23 is not provided, the lip 22 will engage the casing and there will ordinarily be sufficient friction to hold the packer up against the shoulder 24.

The dimensions of the cup 21 are such that it does not intentionally engage the casing as the assembly is being lowered. However, should the friction not be sufiicient to hold the packer up against the shoulder 24, no particular harm is likely to result. Under conditions which cause the packer to occupy the position with respect to the lmandrel shown in FIGURE l, as the plug is being lowered into the well, the cup 21 may strike the casing, but when this occurs, the packer will remain stationary while the mandrel forces the sleeve 13 and wedge body 16 on down, so that there Will be no binding action at this time.

After the limit plug is lowered to the desired location in the well, the tubing 8 and mandrel 'are raised to move the lip 22 into a downwardly extending position whereby the packer 21 will be frictionally held against upward movement relative to the casing 9.

The pumping of cement slurry down through the tubing and mandrel may then be carried on.

As the pressure of the pump is exerted on the slurry, the fiuid pressure below the swab cup 20 will cause it and the wedge body 16 to rise, wedging the packer 21 and lip 22 tightly against the casing 9 whereby the limit plug is tightly set therein. To make certain that the valve 19 is held open by the stinger 12, the tubing 8 is lowered slightly and the parts of the limit plug will then take the relative positions shown in FIGURE 2.

The mandrel '10, 11, 12 must move upwardly slightly to permit the packer to take the position shown in FIG- URE 2. The pump pressure may be sufl'icient to move the mandrel and tubing upwardly to accomplish this, or 'the tubing may be lifted by the rig during the pumping of the slurry.

The -friction between the lip 22 and the casing will prevent the packer from moving upwardly as the wedge body 16 moves upwardly. i

It will be observed that as the wedge body '16 moves upwardly, -it pushes the packer upwardly, slightly, until the lip 22 snaps from the upwardly -directed position shown in FIGURE l to the downwardly directed position shown in FIGURE 2. When this happens, upward movement of the packer is arrested, the lip 22 and the upper portion of the cup 21 being squeezed or wedged in between the upper portion of the wedge 16 and 'the casing 9.

It will be understood that FIGURES 2 and 3 are intended to illustrate the relative positions of the parts 16, 21 'and 22 when the packet is set in the casing, more than the actual shape of the parts under this condition. In actual practice the parts 21 and 22 are probably compressed into a solid mass.

"While rubber (and like equivalent flexible material) has some of the properties of a fiuid when subjected to the high differential pressures encountered in oil well cementing, and while the reasons for the gripping action attained with the packer of the present invention are perhaps not fully understood, experience has shown that the arrangement of lip 22 and cup 21 provides sufficient friction with the casing to hold the sleeve 13 and Wed-ge body 16 against upward movement even though high fiuid pressure is exerted upon it, so that the old conception that metal slips are necessary has been shown to be incorrect.

When the upwardly directed cup 23 is provided on the packer (which, as stated above, is not necessary) if there is liquid in the annular space between the tubing and casing albove the limit plug, this cup serves as a hacking to prevent upward movement of the packer while it is being set.

Once upward movement of the packer is arrested, the swab cup 20 cannot move upwardly any farther, and it serves to prevent the slurry from fiowing upwardly on the outside of the sleeve 13.

Of course, in addition to gripping the casing, the lower portion of the cup 21 serves to prevent upward flow around the outside of the sleeve 13. However, it should 'be pointed out that the main function of the wedge 16, the cup 21 and the lip 22 is to hold the sleeve 13 and wedge 16 against upward movement by gripping the caS- ing. The lbody made up of the cup 21 and lip 22 has been called a packer, for want of a better descriptive term, and it is intended that the word be regarded in the sense of providing material to :completely fill or compact in the space 'between the wedge body 16 and the casing 9 in addition to the usual engineering connotation of means for efiiecting a seal.

After the pumping operation is completed, but before the cement has set, the tubing 8 and mandrel are raised. As the reduced portion 15 of the tension ring 14 comes apart, the parts of the limit plug may take the position shown in FIGURE 3.

In FIGURE 3, it will Ibe seen that the packer is still firmly gripping the casing 9, there having been no upward movement of the wedge body 16, the sleeve 13' or the cup 21 and lip 22.

To insure the proper breaking of the reduced portion 15, the hammer 26, comprising a flange portion of section 11, and anvil 25 have been provided so that some jar blows can be delivered to the tension ring 14, `but this structure is not 'necessary in all cases. In its broader aspects, the invention is not limited to the provision of a jar for the coupling 14. The upper end of ring 14 could be firmly fixed to the section 10 of the mandrel.

In 'FIGURE 3, the upper portion of the ring 14 iS shown located some distance above the hammer 26. This position illustrates the fact that a jar 'blow on the anvil 25 has given the upper portion of the ring 14 some momentum after the reduced portion 15 parted. Of course, if the portion 15 parted under the influence of straight pull, the anvil 25 would probably rbe `resting directly on the hammer 26 instead of being in the raised position shown.

As the tubing 8 and mandrel are raised, the valve 19 closes as mentioned above. The limit plug then holds the slurry 'below it in place until it hardens. The tubing 8 and mandrel can be raised on up above the position shown in FIGURE 3, and the portion of the well bore above the sleeve 15 washed out.

While only one embodiment of the invention has been shown and described herein, it will fbe understood that various changes may be made without departing from the spirit of the invention or the scope of the annexed claims.

I claim: r

\1. A well casing limit plug comprising: a flexi-ble cylin- 'drical packer secured to said plug, terminating at its lower end with a downwardly extending, outwardly flared cup, and having a flexible flange disposed above said cup; said flange having an outside diameter larger than the inside `diameter of a well casing in which said limit plug is inserted and being disposed to bend down and 'overlap an upper portion of said cup between said cup and said casing when said 'cup is raised within said casing; a wedge body disposed beneath said cup, tapering toward said cup, and slidea'ble thereinto for expanding said cup and compressng said cup and said flange against said casing;

means for moving said wedge 'body into said cup to expand it laterally into tight fitting en'gagement with said conduit; a mandrel slideably mounted Within said wedge body; an outwardly extending flange portion mou'nted on said mandrel; and retaining means on said wedge body engaging said fiange portion of vsaid mandrel to permit limited longitudinal movement between said mandrel and said wedge body, said retaining means being releasable under tension applied by upward movement of said mandrel within said Wedge body.

2. A limit plug as defined in claim 1 Wherein said flexble cylindrical packer is slidea'bly mounted on said plug.

3. A limit plug as 'defined in claim 1 wherein said means for moving said Wedge body comprises a second downwardly facing resilient cup secured to said wedge body below said wed'ge 'body and in engageable rela tion with said casing for forcing said wedge body upwardly to set said Packer in response to fluid pressure exerted 'beneath said second cup.

4. A limit plug as defined in claim 1 including a check valve located at the lower end of said Wedge body for preventng upward flow of fiuid through said wed'ge body after said limit plug has been set and said mandrel has been removed.

References Cited in the file of this patent UNITED STATES PATENTS 1,262,107 Sheasley Apr. 9, 1918 2,507,262 McGivern May 9, 1950 2,606,618 Page Aug. 12, 1952 2,815,817 Conrad Dec. 10, 1957 2,833,352 Lloyd May 6, 1958 

